Motor-control system for electric vehicles.



M. R. HANNA. MOTOR CONTROL SYSTEM FOR ELECTRIC VEHICLES. APPLICATIONFILED MAR. 16, 1908.

905,697. Patented Dec. 1, 1908.

Witnesses Inventor:

max R. Hanna,

UNITED STATES PATENT onnrcn MA-X R. HANNA. OF SOHENEGTADY, NEW YORK,ASSIGNOR TO GENERAL ELEGTRIG COMPANY. A CORPORATIQN OF NEW YORK.

MOTOR*CONTROL SYSTEM FOR ELECTRIC VEHICLES.

Specification of Letters Patent.

Patented Dec. 1-, 1908.

Application filed March 16, 1908. Serial No. 421,413.

To a llwhom it may concern:-

Be it known that I, MAXR. HANNA, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Motor-Control S *stemsfor Electric Vehicles, of which the flillowing is a specification.

My invention relates to systems of motor control and more particularlyto devices adapted for the regulation of motors employed for the drivingof vehicles such as railway cars.

It has been found in practice that in starting electrically drivenvehicles which are provided with two or more driving motors the wheelsdriven by one of the motors may slip and the speed of this motortherefore becomes different from the speed of the other motor or motorson the car. This slipping of one pair otwheels maybe due to a variety ofcauses such as ine ualities in the track, variations in the sur ace ofthe car wheels, the presence of ice, water, oil, leaves, etc., on therails. When the wheels driven by a motor begin to slip the coefficientof friction between the wheels and the rails immediately decreases verymuch and the slipping when once started, therefore, tends to continue.If the motors of a car are connected in series when the wheels driven byone of them slip, the increased counterelectromotive force of thatmotor, because of its increased speed, cuts down the current flowing toall the motors and acts to decrease the speed of the motors whose wheelsare not slipping. The decrease in speed of the last mentioned motorscauses a decrease in the counter electromotive force produced by themand a corresponding increase in the potential applied to the m0- tordriving the slipping wheels, with a resulting tendency to furtherincrease the speed of that motor. It is ap arent, .therefore, that whenonce the whee s driven b a motor begin to slip the tendency is for thatmotor to speed up and for the other motors in series with it to slowdown, even, perhaps, until all the motors of the car but one are at restandthat one is, therefore, receiving nearl the full line potential. Thusa motor may have applied to it a potential much in excess of that forwhich it was designed and a flash over or arcing from brush to brush mayresult.

While slipping of the wheels of one motor with respect to the wheels ofthe other Inotor may occur on cars equipped with only two motors, thedanger of a flash over under this condition is small since each mo: toris designed to stand full line potential and, therefore, even if onemotor should speed up and the other one entirely stop the potentialapplied to the slipping motor would not be in excess of that for whichit was designed. The danger, however, becomes much greater with carsequipped with ,four motors arranged in two groups of two each, themotors in each group being permanently connected in series, each motorbeing designed for one-half the line potential. Under this condition if,in starting while all four motors are in series, the wheels of one ofthem slip the other three motors at once tend to slow down and thepotential applied to the motor driving the slippin' w ieels may risenearly to full line potentia or almost twice as high as the potentialfor which the motor was designed. Or if, with an equipment of this kindwhen the airs of motors are in parallel relation, the w eels of a motorof one of the pairs begins to slip, the speed of the other motor in thatpairis immediately decreased and nearly full line potential is appliedto the motor driving the slipping wheels.

In order to prevent injury to the motors, under the above describedcondition, it has been proposed heretofore to use a differential relayarranged to operate when the wheels driven by one motor slip and inoperating to interrupt the control circuits to all the contactors,thereby causing them to drop and interrupt the motor circuits and breakthe connection of the motors with the line. I have found, however, thatsince the slipping of a pair of wheels is but a momentary condition itis not necessary to interrupt the connection of the'motor circuits withthe source of current supply. It is quite sufficient if the motorcircuits be restored to their slowest speed condition withoutinterrupting their connection with the source of supply, if the slippingtakes place while any other condition of the motor circuits exists. Inmy arrangement, therefore,

Which lead to the switches which connect the circuits to the source ofcurrent supply and arrange the motors in series if'at any time thevoltage at the source fails, as may often happen by the currentcollecting device leaving the trolley or third rail, or by this deviceengaging a section of trolley or third rail which is not energized. Ihave, therefore, in carrying out my present invention combined with thislast mentioned arrangement differential relays so arranged that theywill interrupt the same circuit as that interrupted by the no-voltagerelay just mentioned.

My present invention comprises, therefore, in a motor control system,means for interrupting all the control circuits except those motorcircuits to the source of current supply and those which arrange themotors in the 'series or starting positionif while the motor circuitsare in any other condition the speed of one of the motors becomesdifferent from that of the other motors, or if the voltage at the sourcefails.

My invention is, as has been stated, especially useful in connectionwith four motor equipments in which the motors are arranged in pairswith the motors of each pair permanently connected in series, and it isin connection with an equipment of this kind that I have illustrated apreferred embodimerit thereof.

The single figure of'th'e drawing shows diagrammatically a motor andcontrol equipment, adapted to form one unit of a train,

having my invention applied thereto.

The control system which I have illustrated is exactly the same as thatshown in the patent to George H. Hill, No. 815,826, dated March 20,1906, except that in place of each motor shown in his patent, I havesubstituted two motors having their armatures and field coilspermanently connected in series, and except that my invention is appliedthereto in a manner hereinafter described.

A detailed description of the controlsystem which I have shown, in sofar as it is similar to the one illustrated in the patent abovementioned, is unnecessary. It is quitesufficient to point out thevarious elements of the system by the names applied to them in thepatent above mentioned, and as now generally used in this art.

The armatures of the motors of one pair are indicated at M and Nand theother ling resistances R to it a contact S which connects the pairs ofmotors in series; contacts? and P which make the parallel connectionsfor the pairs of motors; and contact- B which serves to complete abridge connection about the series contact and the resistances beforetheseries contact is broken in changing from series to parallel.

, The throttling and checking relay, generally referred to as thenotching relay, is shown at O.

The reversing switch for determining the direction in which currentpasses through the armatures of the pairs of motors is shown at RS.

At K the master-controller, located at one end of the car, is shown indeveloped form, while at K the master-controller, at the opposite end ofthe car, is indicated in outline.

The trolley or third rail shoe is indicated at T, it being understoodthat the rails or ground are utilized as a return circuit.

X and X are main switches for the con trol and motor circuitsrespectively.

1, 2, 3, 4 and 5 are train wires by which the master-controllers on thevarious cars of a train may be connected in parallel to the localcontrol circuits of the .several cars, these wires having suitablecouplings f at their ends whereby connection between cars may be made.

Uindicates a cut-out switch which is an ranged between the train wiresand the motor-controller C and the reversing switch KS, means beinprovided for opening this switch on al the cars of a train by closingone of the switches U on any car of the train. The relay is ano-volt-age relay arranged to interrupt the circuit through one of thecontrol wires, and thereby to return the motor-controller O to its"first series condition if at any time current for the motor circuitfails, as for instance by the third rail shoe or trolley T becomingdisengaged from the third rail or trolley wire.

All of the parts just referred to are shown and fully described in thepatent to Hill, No. 815,826, above mentioned.

At V is shown a differential relay, the two coils of which are connectedrespectivelyin shunt to the'armatures M and \i of one pair of motors,and at IN is shown another diflerent'ial relay, the coils of which areconnected respectively in shunt to the armatures M and bl of the otherpair of motors.

The coils of each relay V and W are so wound and arranged that when thecounter electro- Q is located, thereby afiecting motive force of thearmatures to which-they are connected and therefore the current in fieldacting on the core of each relay will be practically zero. When,therefore, both L motors of a pair are running at the same rate of speedand, therefore, producing the same counter electromotive forces, thedifferential relay connected to them will not pull up.

The differential relays V and W bridge contacts in the same controlcircuit as that controlled by the no-voltage relay The operation of thecontrol system shown is, except for the action of the differentialrelays V and W, fully set forth in the patent to Hill, No. 815,826, andneed not be redescribed. As longas the'motors in eachpair drive thewheels attached to them without slipping upon the track the system will0 erate exactly as does that shown in the ill patent. If, however, thewheels driven b one of the motors of either pair sli the di ferentialrelay V or W connecte to that pair of motors will pull up and interruptthat control circuit in which the no-voltage relay the motor circuits inexactly the same manner as if the relay Q had dropped, due tointerruption of the motor su' )ply circuit. In other words, if thewheels riven by a motor of either pair slip the correspondingdifferential relay V or W acts to interrupt all the control circuitsexcept those controlling the switches which connect the motors to thesource of current and arrange the pairs of motors in series.

When the wheels driven by any motor slip,

voltage relay Q to protect the motors under certain conditions whichoperation.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. In combination, a plurality of motors or groups of motors,resistances for insertion in the motor circuits, a plurality ofelectrically controlled switches for connectin said motors to a sourceof current,for regu ating the amount of resistance in the motor circuitsand for connecting the motors or groups of motors in series and inparallel, a master-controller, control circuits for interconnecting saidmaster-controller and said switches, and means for restoring the motorcircuits to the series arrangement of the motors or groups of motorswith all the resistmay arise during ance in circuit without opening theline,

2 of motor current fails, or if the speeds of the I motors becomedifferent. the coils are the same, the resultant magnetic 2. Incombination, a plurality of motors or groups of motors, resistances forinsertion in the motor circuits, a plurality of electricallycontrolledswitches for connecting said motors to a source of current,for regulating the amount of resistance in the motor cir cuits and forconnecting the motors or groups of motors in series and in paralleh'amaster-controller, control circuits for interconnecting saidmaster-controller and said switches, and means for interrupting all thecontrol circuits except those controlling the switches which connect themotors to the source of current and arrange the motors or groups ofmotors in series if at any time the voltage at the sourceof'motorcurrent fails or if the speeds of the motors become different.

3. In an electrically driven vehicle, two pairs of motors, themotors ofeach pair being permanently connectedin series, resistances or insertionin the motor circuits, a plurality of electrically controlled switchesfor connecting said pairs of motors to a source of current, forregulating the amount of resistance in the motor circuits and forconnecting the pairs of motors in series and in parallel, amaster-controller, control circuits for interconnecting saidmaster-controller and said switches, and means for restoring the motorcircuits to the series arrangement of the pairs of motors with all theresistance in circuit without disconnecting the motor circuits from thesource if while the motor circuits are in any other condition thevoltage at the source of motor current fails or if the s eeds of themotors in either pair become ifiereht.

4. In an electrically driven vehicle, two pairs of motors, the motors ofeach pair being permanently connected in series, resistances orinsertion in the motor circuits, a plurality ofelectrically controlledswitches for con-- necting said pairs of motors to a source of current,for regulating the amount of resistance in the motor circuits and forconnecting the pairs of motors in series and in parallel, amaster-controller, control circuits for interconnecting saidmaster-controller, and said switches, and means for interruptin all thecontrolcircuits except those contro ing the switches which connect themotor circuits to the source of current and arrange the airs of motorsin series if at any time the v0 ta e at the source of motor currentfails or the apeeds of the motors in either pair become ifierent. i

5. In an electrically driven vehicle, two pairs of motors, the motors ofeach pair being permanently connected in series, resistances orinsertion in the motor circuits, 'a plurality of electrically controlledswitches for connecting said pairs of motors to a source of current, forregulating the amount of resistance in the motor circuits and forconnecting the pairs of motors in series and in parallel, amaster-controller, control circuits forinterconnecting saidmaster-controller and said switches, and differential relays eachoperative upon the speeds of the motors in either of the pairs becomingdifferent and arranged to interrupt all the control circuits exceptthose which control the switches which connect the motor circuits to thesource of current and arrange the pairs of motors in series.

6. In an electrically driven vehicle, two pairs of motors, the motors ofeach pair being ermanently connected in series, resistances torinsertion in the motor circuits, a plurality of electrically controlledswitches for connecting said pairs of motors to a source of current, forregulating the amount of resistance in the motor circuits and forconnecting the pairs of motors in series and in parallel, amaster-controller, control c1rcu1ts for mterconnecting saidmaster-controller and sa1d switches, a relay arranged to interrupt allthe control circuits except those controlling the switches which connectthe motor circuits to the source of current and arrange the pairs ofmotors in series if at any time the volta e at the source of motorcurrent fails, and iifierential relays each operative upon the s eeds ofthe motors in either of the pairs ecoming difierentand arranged tointerrupt the same circuits as does the first mentloned relay.

In witness whereof, I have hereunto set my hand this 14th day of March,1908.

MAX R. HANNA.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

